The present invention relates to a solvent free, diluent free, hydrocarbon soluble liquid colorant, as well as a method for applying the colorant to solid granular substrates. More specifically, the invention includes a method for applying a liquid colorant to fertilizer to provide a colored fertilizer where the colorant exhibits a reduced tendency to bleed or migrate from the surface of the fertilizer onto other substrates. Colored fertilizer is useful in many applications where it is necessary to see where the fertilizer has already been applied, so that an even coating-may be applied to a specific area. If too much fertilizer is added to a lawn, for instance, the grass may die as a result. If too little fertilizer is added, the desired result of healthy grass is not achieved.
Heretofore, methods of coloring solid granular substrates, such as fertilizer containing hydrocarbon components for use as binders or dedusting agents, have included the use of pigments and solvent dyes. These colorants are generally diluted with a polybutene and sprayed onto the fertilizer. The polybutene, which serves primarily as a dedusting agent, also disperses the color and helps to bind the active ingredients of the colorant to the fertilizer. Solvent dyes or pigments, which have been dissolved or emulsified in some solvent or diluent, are generally added to a dedusting agent, such as polybutene, and are then sprayed onto the fertilizer. Optionally, an herbicide, such as Atrazine, may be added to the fertilizer. The use of such colorants presents certain problems. First, solvent dyes tend to stain the plastic bags that are used to package the fertilizer. Also, if the colorant contains any constituents that are hydroscopic, the fertilizer tends to clump and cause processing problems in the bagging process. Pigments provide non-migrating colors, but are generally not soluble in a dedusting agent or binder. Solvents, on the other hand, are soluble in the dedusting agent or binder, but have the migration problems mentioned above.
Thus, it would be advantageous to provide a liquid, polymeric, non-staining colorant that is soluble in a hydrocarbon medium, and which contains no hydroscopic components. Further, it would be advantageous to provide a method for coloring fertilizer that eliminates or significantly reduces the use of solvents and diluents, which may be harmful to the environment, and which add substantial cost to the coloring process.
Accordingly, it is an object of the present invention to provide a solvent free, diluent free, hydrocarbon soluble liquid polymeric colorant that may be applied directly to a solid granular substrate, such as fertilizer, where the colorant has a reduced tendency to migrate into or onto other substrates.
It is another object of the present invention to provide a liquid polymeric colorant that may be applied to fertilizer without the use of solvents or diluents.
Yet another object of the present invention is to provide a liquid polymeric colorant having low viscosity in pure form.
Still another object of the present invention is to provide a method for coloring solid granular substrates so that the colorant does not migrate off of the substrates and stain other surfaces with which it comes into contact.
Another object of the present invention is to provide a method for coloring solid granular substrates, such as fertilizer, that eliminates the use of solvent dyes and pigments, and also eliminates or significantly reduces the use of solvents and diluents.
Yet another object of the present invention is to provide a method for coloring fertilizer that is less costly than other coloring methods, and which avoids other problems associated with current techniques for coloring fertilizer.
These and other aspects and advantages of the present invention will become apparent in the specification and the appended claims.